Magnetic resonance imaging apparatus and magnetic resonance imaging method

ABSTRACT

An MRI apparatus includes an imaging data acquiring unit and a blood flow information generating unit. The imaging data acquiring unit acquires imaging data from an imaging region including myocardium, without using a contrast medium, by applying a spatial selective excitation pulse to a region including at least a part of an ascending aorta for distinguishably displaying inflowing blood flowing into the imaging region. The blood flow information generating unit generates blood flow image data based on the imaging data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of copending application Ser. No.12/763,643 filed Apr. 20, 2010, which claims priority based uponJapanese Patent Application No. 2009-216890 filed Sep. 18, 2009, theentire contents of which are hereby incorporated by reference.

This application is also related to copending and commonly owned Ser.No. 12/946,549 filed Nov. 15, 2010.

BACKGROUND

1. Technical Field

The subject disclosure relates to MRI (magnetic resonance imaging) thatmagnetically excites nuclear spins of an object with an RF (radiofrequency) signal having the Larmor frequency and reconstructs an imagebased on NMR (nuclear magnetic resonance) signals generated due to theexcitation.

More particularly, the subject disclosure relates to a magneticresonance imaging apparatus and a magnetic resonance imaging method thatcan perform MRA (Magnetic Resonance Angiography) for acquiring a bloodflow image without using a contrast medium.

2. Description of Related Art

Magnetic Resonance Imaging is an imaging method that magneticallyexcites nuclear spins of an object set in a static magnetic field withan RF signal having the Larmor frequency and reconstructs an image basedon NMR signals generated due to the excitation.

In the field of the magnetic resonance imaging, MRA is known as a methodof obtaining an image of a blood flow. An MRA without administration ofcontrast materials is referred to as a non-contrast MRA (for example,refer to Japanese Publication of Patent Application No. 2001-252263). Asthe non-contrast MRA, an FBI (fresh blood imaging) method has beendevised. In the FBI method, an ECG (electrocardiogram) synchronizationto capture a fast blood flow pumped by a heart is performed, and therebya blood vessel is satisfactorily depicted.

Meanwhile, MR (Magnetic Resonance) perfusion and delayed enhancement areconventionally used for examining an ischemic part and an infarcted partin heart. In the conventional cardiac study, cardiac perfusion anddelayed enhance MR imaging are performed under a contrast-enhanced (CE)MRA method in which a patient is given a contrast medium afterundergoing medicational stress or exercise stress for the perfusionstudy.

FIG. 1 shows a cross-section of myocardium for explaining theconventional cardiac study method that uses CE MRA. When dynamic imagingis performed by administering a gadolinium-based contrast medium to apatient, the level of the signal from “tissue A” becomes high. This isbecause blood flows into “tissue A” which is supplied with blood bynormal blood vessels inside the myocardium as shown in FIG. 1. However,in a state in which blood vessels are dilated under medicational stressor exercise stress, a region of low signal level appears as “ischemicpart B”, because blood flow volume decreases relatively due to stenosedblood vessels. Therefore, the region of the low signal level can bediagnosed as “ischemia is indicated as B”. In this way, ischemia test isalso called stress perfusion and it can detect an ischemic part as adefect of vascular circulation by administering a contrast medium to apatient under medicational stress or exercise stress.

Additionally, a late delayed enhanced (LDE) technique is known as amethod for the diagnosis of infarction. The LDE is a diagnosis methodwhich allows a contrast medium to flow into the myocardium tissue, andthereby diagnoses the part without a function to wash out the contrastmedium as the infarction. For example, in “infarction part C” whereblood vessels are occluded as shown in FIG. 1, the contrast mediumremains within the part C, because the tissue doesn't have the functionto wash out the contrast medium. Thus, LDE occurs due to the residualcontrast medium, and it enables the detection of “infarction part C” asa region of high signal level as compared to the normal “tissue A” wherethe contrast medium is washed out.

A cardiac examination is also performed in other diagnostic imagingunits and its results are displayed in various display methods. Forexample, technology to display a myocardium layer of differentcross-sections by using cardiac CT image data acquired with X-ray CT(computed tomography) apparatus is known. Also, technology to display across-sectional image of myocardium in a bulls-eye method by usingcardiac 3-dimensional image data acquired using ultrasonograph (US) isknown (for example, refer to the Japanese Publications of PatentApplication Nos. 2006-198411 and 2005-531352).

However, in the conventional cardiac examination using an MRI apparatus,ischemic and infarct parts are diagnosed by performing dynamic imagingafter injection of gadolinium-based contrast materials under influenceof medicational stress or exercise. Therefore, imaging timing isrestricted to the period where contrast medium is washed-out in thenormal tissue and still in the infarction area after administering acontrast medium, otherwise sufficient contrast can not be obtained.Thus, it has a limit in terms of temporal resolution as a problem.Additionally, spatial resolution also degrades due to the restriction oftime resolution. Under the aforementioned technical background, there isa problem that image quality varies and diagnosis varies among readers.

Moreover, the relationship between the gadolinium-based contrast mediumand Nephrogenic Systemic Fibrosis (NSF) is concerned due to a black-boxwarning from the FDA (Food and Drug Administration). Furthermore, instress perfusion test, risk of medication such as adenosine anddipyridamole is also a huge concern. The aforementioned problems applyto a case in which CE MRA imaging is acquired for various imagingregions.

BRIEF SUMMARY

The present disclosure aims to provide MRI technology which can safelyacquire “MRA imaging region including a heart” and “blood flowinformation based on the MRA image” with satisfactory time resolutionand spatial resolution.

The content of the exemplary embodiments will be described per eachaspect as follows:

(1) According to one aspect of a magnetic resonance imaging apparatus ofthe disclosure, the magnetic resonance imaging apparatus comprises animaging data acquiring unit, a blood flow image generating unit, and acardiac function analysis unit.

The imaging data acquiring unit acquires a plurality of 3-dimensionalimaging data corresponding to mutually different traveling time ofinflowing blood flowing into an imaging region including myocardium insynchronization with a heartbeat without using a contrast medium, byapplying a spatial selective excitation pulse plural times fordistinguishably displaying the inflowing blood and by changing time fromapplication timing of the spatial selective excitation pulse toacquisition timing of the plurality of imaging data.

The blood flow image generating unit generates a plurality of blood flowimage data corresponding to the mutually different traveling time of theinflowing blood based on the plurality of imaging data.

The cardiac function analysis unit acquires blood flow informationindicating cardiac function of the myocardium based on the plurality ofblood flow image data.

(2) According to another aspect of a magnetic resonance imagingapparatus of the exemplary embodiments, the magnetic resonance imagingapparatus comprises an imaging data acquiring unit and a blood flowinformation generating unit.

The imaging data acquiring unit acquires at least one of imaging datafrom an imaging region including the myocardium without using a contrastmedium, by applying a spatial selective excitation pulse to a regionincluding at least a part of an ascending aorta for distinguishablydisplaying inflowing blood flowing into the imaging region.

The blood flow information generating unit generates at least one ofblood flow image data based on the imaging data.

(3) A magnetic resonance imaging method of the exemplary embodimentscomprises the steps of: (a) acquiring imaging data from an imagingregion including the myocardium without using a contrast medium, byapplying a spatial selective excitation pulse to a region including atleast a part of an ascending aorta (cardiac aorta) for distinguishablydisplaying inflowing blood flowing into the imaging region, and (b)generating blood flow image data based on the imaging data.

According to the magnetic resonance imaging apparatus or the magneticresonance imaging method configured as described above, MRA image dataof an imaging region including heart and blood flow information based onthe MRA images can be acquired safely with satisfactory time resolutionand spatial resolution.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional diagram of myocardium for explaining acardiac testing method using conventional contrast-enhanced (CE) MRA;

FIG. 2 is a block diagram showing a magnetic resonance imaging apparatusaccording to one embodiment of the present disclosure;

FIG. 3 is a functional block diagram of the computer 32 shown in FIG. 2;

FIG. 4 is a timing chart showing an example of a time-spatial labelingpulse (time-SLIP) sequence set in the imaging condition setting unit 40shown in FIG. 3;

FIG. 5 is a timing chart showing another example of a time-SLIP sequenceset in the imaging condition setting unit 40 shown in FIG. 3;

FIG. 6 is a diagram showing the first example of a labeling region(labeled region) set in the imaging condition setting unit shown in FIG.3;

FIG. 7 is a diagram showing the second example of a labeling region(labeled region) set in the imaging condition setting unit 40 shown inFIG. 3;

FIG. 8 is a diagram showing the third example of a labeling region(labeled region) set in the imaging condition setting unit 40 shown inFIG. 3;

FIG. 9 is a diagram showing the fourth example of a labeling region(labeled region) set in the imaging condition setting unit 40 shown inFIG. 3;

FIG. 10 is a diagram showing the fifth example of a labeling region(labeled region) set in the imaging condition setting unit 40 shown inFIG. 3;

FIG. 11 is a diagram showing the sixth example of a labeling region(labeled region) set in the imaging condition setting unit 40 shown inFIG. 3;

FIG. 12 is a diagram showing the seventh example of a labeling region(labeled region) set in the imaging condition setting unit 40 shown inFIG. 3;

FIGS. 13A-E are diagrams for explaining the method of determining TI andBBTI set as imaging conditions in the imaging condition setting unit 40shown in FIG. 3;

FIGS. 14A-B are diagrams for explaining the process of generating bloodflow image data executed in the blood flow image generating unit byeliminating signal component except blood from image data;

FIGS. 15A-B are diagrams showing an example of a profile of blood flowimage data generated by the blood flow information generating unit 45shown in FIG. 3;

FIGS. 16A-D are diagrams showing an example of a set of profiles ofblood flow image data corresponding to a plurality of different BBTIsgenerated by the blood flow information generating unit 45 shown in FIG.3;

FIG. 17 is a diagram showing an example of distinguishably displayedlesion areas of myocardium identified by the blood flow informationgenerating unit 45 shown in FIG. 3 based on signal differences betweenblood flow image data corresponding to different black blood inversiontimes (BBTIs);

FIG. 18 is a diagram showing a signal difference in the line ROI-Acrossing the ischemic area shown in FIG. 17;

FIG. 19 is a diagram showing signal difference in the line ROI-Bcrossing the infarction area shown in FIG. 17;

FIG. 20 is an example showing how the blood flow information generatingunit 45 shown in FIG. 3 enables users to select display of each signaldifference value between blood flow image data corresponding todifferent BBTIs in a plurality of line ROIs on a cross-section ofmyocardium;

FIG. 21 is a diagram showing reference positions for the blood flowinformation generating unit 45 shown in FIG. 3 to perform positionalcorrection between blood flow image data; and

FIG. 22 is a flowchart showing a procedure for acquiring blood flowinformation on cross-sections of myocardium of an object P anddisplaying their images by performing a non-contrast MRA imaging withthe magnetic resonance imaging apparatus 20 shown in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

A magnetic resonance imaging apparatus and a magnetic resonance imagingmethod according to embodiments of the exemplary embodiments will bedescribed with reference to the accompanying drawings.

(Configuration and Function)

FIG. 2 is a block diagram showing a magnetic resonance imaging apparatusaccording to one embodiment of the present disclosure.

A magnetic resonance imaging apparatus 20 includes a cylinder-shapedstatic magnetic field magnet 21 for generating a static magnetic field,a cylinder-shaped shim coil 22 arranged inside the static magnetic fieldmagnet 21, a gradient coil 23 and RF coils 24.

The magnetic resonance imaging apparatus 20 also includes a controlsystem 25. The control system 25 includes a static magnetic field powersupply 26, a gradient magnetic field power supply 27, a shim coil powersupply 28, a transmitter 29, a receiver 30, a sequence controller 31 anda computer 32. The gradient magnetic field power supply 27 of thecontrol system 25 includes an X-axis gradient magnetic field powersupply 27 x, a Y-axis gradient magnetic field power supply 27 y and aZ-axis gradient magnetic field power supply 27 z. The computer 32includes an input device 33, a display device 34, an operation device 35and a storage device 36.

The static magnetic field magnet 21 is electrically connected to thestatic magnetic field power supply 26 and has a function to generate astatic magnetic field in an imaging region by using electric currentsupplied from the static magnetic field power supply 26. The staticmagnetic field magnet 21 includes a superconductivity coil in manycases. The static magnetic field magnet 21 gets electric current fromthe static magnetic field power supply 26 which is electricallyconnected to the static magnetic field magnet 21 at excitation. However,once excitation has been made, the static magnetic field magnet 21 isusually isolated from the static magnetic field power supply 26. Thestatic magnetic field magnet 21 may include a permanent magnet whichmakes the static magnetic field power supply 26 unnecessary.

The cylinder-shaped shim coil 22 is coaxially arranged inside the staticmagnetic field magnet 21. The shim coil 22 is electrically connected tothe shim coil power supply 28. The shim coil power supply 28 supplieselectric current to the shim coil 22 so that the static magnetic fieldbecomes uniform.

The gradient coil 23 includes an X-axis gradient coil 23 x, a Y-axisgradient coil 23 y and a Z-axis gradient coil 23 z. Each of the X-axisgradient coil 23 x, the Y-axis gradient coil 23 y and the Z-axisgradient coil 23 z is cylinder-shaped and arranged inside the staticmagnetic field magnet 21. A bed 37 is arranged inside the gradient coil23 and the area inside the gradient coil 23 is an imaging area. The bed37 supports an object (e.g., a patient) P. The RF coils 24 include a WBC(whole body coil) built in the gantry for transmission and reception ofRF signals and local coils arranged around the bed 37 or the object Pfor reception of RF signals.

The gradient coil 23 is electrically connected to the gradient magneticfield power supply 27. The X-axis gradient coil 23 x, the Y-axisgradient coil 23 y and the Z-axis gradient coil 23 z of the gradientcoil 23 are electrically connected to the X-axis gradient magnetic fieldpower supply 27 x, the Y-axis gradient magnetic field power supply 27 yand the Z-axis gradient magnetic field power supply 27 z of the gradientmagnetic field power supply 27 respectively.

The X-axis gradient magnetic field power supply 27 x, the Y-axisgradient magnetic field power supply 27 y and the Z-axis gradientmagnetic field power supply 27 z supply electric currents to the X-axisgradient coil 23 x, the Y-axis gradient coil 23 y and the Z-axisgradient coil 23 z respectively so as to generate gradient magneticfield Gx in the X-axis direction, gradient magnetic field Gy in theY-axis direction and gradient magnetic field Gz in the Z-axis directionin the imaging area.

The RF coils 24 are electrically connected to the transmitter 29 and/orthe receiver 30. The transmission RF coil 24 has a function to totransmit a RF signal given from the transmitter 29 to the object P. Thereception RF coil 24 has a function to receive an NMR signal generateddue to excited nuclear spin inside the object P by the RF signal andgive the received NMR signal to the receiver 30.

The sequence controller 31 of the control system 25 is electricallyconnected to the gradient magnetic field power supply 27, thetransmitter 29 and the receiver 30. The sequence controller 31 has afunction to storage sequence information describing control informationneeded in order to make the gradient magnetic field power supply 27, thetransmitter 29 and the receiver 30 drive. The aforementioned controlinformation includes motion control information, such as intensity,impression period and impression timing of the pulse electric currentwhich should be impressed to the gradient magnetic field power supply27. The sequence controller 31 also has a function to generate gradientmagnetic fields Gx, Gy and Gz in the X-axis, Y-axis and Z-axisdirections and RF signals by driving the gradient magnetic field powersupply 27, the transmitter 29 and the receiver 30 according to apredetermined sequence stored.

The sequence controller 31 is also configured to receive raw data, whichare complex data obtained through the detection of an NMR signal and A/Dconversion to the NMR signal detected in the receiver 30, and input theraw data to the computer 32.

Therefore, the transmitter 29 has a function to give an RF signal to thetransmission RF coil 24 in accordance with the control informationprovided from the sequence controller 31. The receiver 30 has a functionto generate raw data which are digitized complex number data obtained bydetecting an NMR signal given from the reception RF coil 24, performingpredetermined signal processing to the NMR signal detected, andperforming A/D conversion to the NMR signal after the predeterminedsignal processing. The receiver 30 also has a function to give thegenerated raw data to the sequence controller 31.

In addition, the magnetic resonance imaging apparatus 20 comprises anECG unit 38 for acquiring an ECG (electrocardiogram) signal of theobject P. The ECG signal detected by the ECG unit 38 is outputted to thecomputer 32 through the sequence controller 31.

Note that a PPG (peripheral pulse gating) signal representing a cardiacbeat as pulse wave information may be acquired instead of the ECG signalrepresenting a cardiac beat as heart rate information. A PPG signal isacquired by detecting a pulse wave of, e.g., a tip of a finger as anoptical signal. When a PPG signal is acquired, a PPG signal detectionunit is provided with the magnetic resonance imaging apparatus 20.Hereinafter, a case of acquiring the ECG signal will be described.

The computer 32 obtains various functions by the operation device 35executing some programs stored in the storage device 36 of the computer32. Alternatively, some specific circuits having various functions maybe provided with the magnetic resonance imaging apparatus 20 instead ofusing some of the programs.

FIG. 3 is a functional block diagram of the computer 32 shown in FIG. 2.

The computer 32 functions as an imaging condition setting unit 40, asequence controller control unit 41, a k-space database 42, a blood flowimage generating unit 43, an image database 44 and a blood flowinformation generating unit 45. The imaging condition setting unit 40comprises a prescan condition setting unit 40A, an imaging parameter isdetermining unit 40B and an imaging parameter storing unit 40C.

The imaging condition setting unit 40 has a function to set imagingconditions including a pulse sequence based on instructions from theinput device 33 and to provide the set imaging conditions to thesequence controller control unit 41. Additionally, the imaging conditionsetting unit 40 has a function to set a pulse sequence to acquire ablood flow image on a cross-section of myocardium by labeling (tagging)blood flowing into an imaging region under ECG synchronization withoutusing a contrast medium. The imaging condition setting unit 40 also hasa function to set a plurality of pulse sequences to acquire a pluralityof blood flow images, each of which is indicative of mutually differenttraveling time of labeled blood. Note that the term “label” or“labeling” as used herein is synonymous with “tag” or “tagging”,respectively.

As an imaging sequence for acquiring data from an imaging regionincluding a plurality of cross-sections of myocardium, for example, athree-dimensional (3D)—fast spin echo (FSE) sequence, a 3D—fastasymmetric spin echo or fast advanced spin echo (FASE) sequence, a 3Dsteady state free precession (SSFP) sequence, an echo planar imaging(EPI) sequence and a radial data acquiring sequence can be used.

The FASE sequence is an FSE-type sequence which utilizes a half-Fouriermethod.

The radial data acquiring sequence includes a Periodically RotatedOverlapping Parallel Lines with Enhanced Reconstruction (PROPELLER)sequence which rotates a plurality of data acquiring lines.

The SSFP sequence has different versions such as a balanced SSFPsequence (or a true SSFP sequence). The balanced SSFP sequence and thetrue SSFP sequence are suitable for fast data acquisition because oftheir high efficiency of data acquisition.

The FBI method is known as non-contrast-enhanced MRA. The FBI method isa non-contrast-enhanced MRA which uses a sequence such as a FASEsequence to acquire echo data repeatedly every plural heartbeats at thetiming delayed by a predetermined time from a trigger signal. Thistrigger signal is synchronized with a reference wave, such as an R wave,indicative of a cardiac time phase of the object P.

According to the FBI method, a transverse relaxation (T2) component ofmagnetization in blood recovers with elapse of plural heartbeats,thereby water (blood) weighted imaging, in which the T2 magnetizationcomponent of blood is enhanced, can be obtained as a blood vessel image.Moreover, three dimensional imaging for acquiring echo data (volumedata) for predetermined slice encode amounts is performed in the FBImethod.

Furthermore, imaging conditions for labeling blood are set in order todepict blood flowing from an aorta into an imaging region inside theheart satisfactorily. As one of labeling methods, a Time-SLIP (TimeSpatial Labeling Inversion Pulse) method, in which a plurality oflabeling pulses is applied, is known. Hereinafter, the time-SLIP methodwill be described as an example of labeling methods.

In the time-SLIP method, a time-SLIP pulse for labeling is applied inaccordance with the time-SLIP sequence and blood flowing into an imagingregion is labeled. That is, the time-SLIP sequence is an imaging issequence which applies an arterial spin labeling (ASL) pulse forlabeling blood flowing into an imaging section so that the labeled bloodis selectively depicted or suppressed. According to this time-SLIPsequence, signal intensities of only blood reaching the imaging regionafter TI (inversion time) can be selectively emphasized or suppressed.The time-SLIP pulse is applied after a certain delay time from an R waveof an ECG signal. In this case, imaging is performed under ECGsynchronization.

In the time-SLIP sequence, “a spatial non-selective inversion pulse(region non-selective inversion pulse)” and “a spatial selectiveinversion pulse (region selective inversion pulse)” are used. Thespatial non-selective inversion pulse can be switched on/off. Thetime-SLIP sequence includes at least the spatial selective inversionpulse. That is, there are two cases for the time-SLIP sequence. In onecase, the time-SLIP sequence consists of the spatial selective inversionpulse(s) only. In the other case, the time-SLIP sequence includes boththe spatial non-selective inversion pulse(s) and the spatial selectiveinversion pulse(s).

The spatial selective inversion pulse can be set arbitrarily independentof an imaging region. When blood flowing into an imaging region islabeled with the spatial selective inversion pulse, signal intensity atthe part to which the blood reaches after BBTI becomes strong. Note thatwhen the spatial non-selective inversion pulse is set to off, signalintensity at the part to which blood reaches after BBTI becomes weak.Therefore, a moving direction and a distance of blood movement can beunderstood.

FIG. 4 is a timing chart showing an example of the time-SLIP sequenceset in the imaging condition setting unit 40 shown in FIG. 3. In FIG. 4,the abscissa axis indicates passing time t. Additionally, ECG, RF, G andMz in FIG. 4 indicate an R wave as an ECG trigger, an RF signal, agradient magnetic field pulse and longitudinal magnetization component,respectively. Also, td1 is a time period (delay time) from the time ofan R wave to the time of applying a spatial non-selective 180° IR(inversion recovery) pulse. Additionally, td2 is a time period (delaytime) from the time of an R wave just before the starting time of dataacquisition to the time of starting the data acquisition.

As shown in FIG. 4, the spatial non-selective 180° IR pulse is appliedat the timing delayed by the predetermined delay time td1 from the timeof the R wave, in synchronization with the R wave of the ECG signal.Thereby longitudinal magnetization component Mz of myocardium and bloodinside the object P inverts. That is, both of the longitudinalmagnetization components Mz of the myocardium and the blood become −1.

Next, the first and second 180° spatial selective IR pulses are appliedat a different timing each other to a slab selected as a labelingregion. Note that the application timing of the first spatial selective180° IR pulse is ΔT after the application timing of the spatialnon-selective 180° IR pulse. Additionally, in order to select a slab forlabeling, the first and second 180° slab-selective excitation gradientmagnetic field pulses are respectively applied at the same timing as theapplication timing of the first or second spatial selective 180° IRpulse. Thereby, longitudinal magnetization component Mz of blood insidethe labeling region selectively inverts after recovering by the quantityaccording to the time interval between the spatial non-selective 180° IRpulse and the spatial selective 180° IR pulse. That is, the blood insidethe labeling region is labeled.

Note that in FIG. 4, the longitudinal magnetization component Mz of theblood inside the labeling region inverted by the first spatial selective180° IR pulse is shown as a two-dot chain line, whereas the Mz of theblood inverted by the second spatial selective 180° IR pulse is omitted.This is because FIG. 4 becomes complicated if both of them are shown.Meanwhile, the longitudinal magnetization component Mz of blood outsidethe labeling region is maintained as a negative value without beinginverted. That is, the first and second spatial selective 180° IR pulsesfunction as a labeling pulse.

Then, an imaging sequence is started at a timing BBTI after theapplication timing of the 180° spatial non-selective pulse (that is, ata timing BBTI (Black Blood Traveling Time) after the application timingof the first spatial selective 180° IR pulse), and data acquisition ofthe imaging region including the myocardium part is started.

Note that it is preferable to perform the data acquisition at a cardiactime phase of the same diastole consistently, because the myocardium isalways in motion. Then, the delay time td1 and td2 of ECGsynchronization are set so that the data acquisition is performed at anappropriate cardiac time phase at diastole.

More specifically, the heart is the most suitable for data acquisitionin terminal phase at diastole, because its state in terminal phase atdiastole is the closest to static condition due to smaller heartbeat. Inthe exemplary embodiments, images are respectively acquired for mutuallydifferent BBTIs by changing BBTI as will be mentioned later, whereas itis impossible to synchronize the start timing of the data acquisitionwith the terminal phase at diastole by merely increasing BBTI each timeof the data acquisition.

It is desirable to control the delay time td1, td2, and the relationshipbetween the labeling pulse and the region non-selective pulse by meansof satisfying the following two conditions (a) and (b), when BBTI isincreased: (a) is to synchronize the start timing of the dataacquisition with the terminal phase of diastole consistently (throughthe entire data acquisition), and (b) is to start the data acquisitionwhen the longitudinal magnetization component Mz of the unlabeledmyocardium is zero (when the background signal is inhibited).

In order to satisfy the conditions (a) and (b), the exemplaryembodiments enable control of BBTI and inhibition of the backgroundsignal independently by using the following equations (1) and (2):

Td1+ΔT+BBTI=n×RR+td2  (1)

ΔT+BBTI=TI  (2)

In the equation (1), RR is a time interval between an R wave and thenext R wave, “n” is counting number equal to or larger than 1 (forexample, up to 3). FIG. 4 corresponds to the case where n=2. In theequation (2), TI is a physical value determined by longitudinalrelaxation time of the myocardium, and is constant.

Then, in this embodiment, RR is measured based on an ECG signal, then“n” is determined, and then the delay time td2 is determined so as tosynchronize the start timing of the data acquisition with the terminalphase of diastole. When the delay time td2 is determined, the delay timetd1 is unambiguously determined based on the equation (1). Next, ΔT andBBTI are determined based on the equation (2) so that the dataacquisition starts at the same timing as the longitudinal magnetizationcomponent Mz of the unlabeled myocardium becomes zero.

Here, in order to prolong reaching distance of blood, it is necessary toextend BBTI. Therefore, BBTI may be set longer than TI by setting thesign of TI negative. That is, the spatial selective 180° IR pulse may beapplied before the spatial non-selective 180° IR pulse.

Note that a cyclic period of one heartbeat is not always the same value,but changes. Thus, it is preferable to change a pulse sequenceappropriately according to the change in heartbeats. Specifically, RRfor the target of the data acquisition is estimated based on data of ECGsignal, a plurality of RRs prior to the RR for the target of the dataacquisition, and so on. Then, the delay time td2 is controlled(adjusted) based on the estimated value of RR dynamically or inreal-time. In this control (adjustment), it is preferable to avoidperforming the data acquisition or to correct the delay time td2 to avalue shorter than the estimated value of the RR for the target of thedata acquisition, when the estimated value of the RR is extremely short.This is because in the case of the delay time td2 longer than the RR forthe target of the data acquisition, the data acquisition may beperformed in systole and this cardiac time phase is not appropriate fordata acquisition due to larger motion of the heart.

Moreover, a fat suppression pulse such as a fat-saturation pulse, a SPIR(spectral pre-saturation with inversion recovery) pulse and so on isapplied before the data acquisition as shown in FIG. 4.

In the case of the FBI method, the period of the data acquisitionextends for plural heartbeats. Additionally, because the dataacquisition is performed without using a contrast medium, there is notime limit. Therefore, an imaging sequence for performing 3-dimensionaldata acquisition with high resolution can be used.

Note that TI and BBTIs can be set independently of each other. That is,although a time interval ΔT between a spatial non-selective 180° IRpulse and a spatial selective 180° IR pulse is almost zero in theconventional art, the time interval ΔT is changeable in the exemplaryembodiments. Though the time interval ΔT can be set instead of TI orBBTIs, hereinafter, the case of setting TI and BBTIs will be explained.

The longitudinal magnetization components Mz of the myocardium and theunlabeled blood in the imaging region recover after the application ofthe spatial non-selective 180° IR pulse, as shown in FIG. 4. Then, it isdesirable to determine TI so that the data acquisition is started at thesame timing as both of “the absolute value of the longitudinal tomagnetization component Mz of the myocardium functioning as background”and “the absolute value of the longitudinal magnetization component Mzof the unlabeled blood” are equal to or less than a predetermined valueand both are approximately zero. Thereby, unnecessary signals from theunlabeled blood and the myocardium is functioning as a background can beinhibited, whereas signal from the labeled blood can be selectivelyemphasized.

However, recovery rate of the longitudinal magnetization component Mz ofthe myocardium is different from that of blood as shown in FIG. 4. Then,TI is determined in order for the data acquisition to start at thetiming when the longitudinal magnetization component Mz of themyocardium becomes approximately zero. At the same time, the signal fromthe unlabeled blood can be suppressed by performing data processing.Thereby, unnecessary signals from the unlabeled blood and the myocardiumcan be inhibited more sufficiently.

The process of eliminating the signals from the unlabeled blood can beperformed in blood flow image generating unit 43 as discussed later.Specifically, magnetic resonance signals are complex signals. Therefore,when “real image reconstruction processing” is performed by using realparts (not absolute value) of the magnetic resonance signals, themagnetic resonance signals from the unlabeled blood become low in signallevel in image data due to their negative value. Thus, when image datais displayed with luminance according to data values, a labeled bloodpart with high signal level is displayed with high luminance, whereasthe unnecessary unlabeled blood part is displayed with low luminance.Moreover, it is possible to display only the labeled blood selectivelywhitely as white blood, because signal values from the myocardium areapproximately zero.

Moreover, it is possible to make “canonicalized signals of negativevalue from the unlabeled blood”−1 by applying cosine filter to theacquired data. Thereby, it is possible to make the unlabeled blood partblack in the image data displayed with luminance.

Additionally, BBTI can be set so that BBTI extends for pluralheartbeats. In order to achieve this, BBTI can be set longer than TI,that is, ΔT<0. When the spatial selective 180° IR pulse is applied, thelabeled blood in the labeling region moves into the imaging region afterelapse of BBTI. Then, out of signals acquired by the data acquisition,the signal of the labeled blood is especially emphasized. Therefore, ifBBTI can be set longer, blood traveling for a longer distance can beemphasized.

The maximum value of settable BBTI can be increased, when the spatialselective 180° IR pulse is applied plural times. That is, when thelabeling pulse is applied to the labeling region plural times, quantityof the labeled blood increases and thereby the maximum value of settableBBTI becomes longer. In the example shown in FIG. 4, two spatialselective 180° IR pulses are applied. That is, the second spatialselective 180° IR pulse is applied after the application of the firstspatial selective 180° IR pulse.

It is desirable to set ΔBBTI so that the flow of the labeled bloodcontinues uninterruptedly. For example, the maximum value of settableBBTI can be doubled theoretically, if the second spatial selective 180°IR pulse is applied “to the same region as the region applied with thefirst spatial selective 180° IR pulse” at the timing when all of theblood labeled by the first spatial selective 180° IR pulse flows out ofthe labeling region. Note that the region to which the second spatialselective 180° IR pulse is applied may be the same as or different fromthe region to which the first spatial selective 180° IR pulse is applied(both cases can be used in the exemplary embodiments). It is desirableto make the flow of labeled blood consecutive by, for example, setting“the application region of the second spatial selective 180° IR pulse”to “a part of the application region of the first spatial selective 180°IR pulse which is imaging region-side”.

Moreover, single or plural MPP (motion probing pulse) as NMR signals formonitoring in an RMC (real-time motion correction) method can beacquired before data acquisition, if needed. The RMC method is a methodcorrecting “a target region for imaging data” and “acquired data” inreal-time so that influence of respiratory motion is eliminated byacquiring the MPP with ECG-synchronization generally and using motionquantity measured based on the MPP. The imaging condition setting unit40 has the function of correcting an imaging data acquisition regionbased on the RMC method.

The MPP is acquired from a region including, e.g., a diaphragm “withphase encode quantity smaller than that of the imaging data” or “withoutapplying phase encoding gradient magnetic field”. Then, the position ofthe diaphragm regarding a body axial direction at the time of the MPPacquisition can be detected as respiration level based on signalsacquired by performing 1D (one-dimensional) FT (Fourier Transformation)on the MPP. Thereby, variation (fluctuation) from a reference value ofrespiratory level can be determined as respiratory motion quantity(motion quantity caused by respiration). Moreover, the influence of therespiratory motion can be suppressed, if the data acquisition region ismoved by the distance corresponding to the respiratory motion quantity.

Additionally, it is possible to visualize time change of the respiratorylevel and avoid performing data acquisition, when the respiratory levelgoes out of acceptable level. Moreover, phase correction and positionalcorrection of imaging data may be performed according to the respiratorymotion quantity as post-processing for eliminating the influence of therespiratory motion.

Note that the data acquisition may be performed under the state ofarrested respiration by making the object P do breath hold with orwithout the use of the RMC.

Next, another example of the time-SLIP sequence will be explained.

Generally, BBTI value is from 1200 ms (milliseconds) to 1400 ms and TIvalue is about 600 ms in many cases. Therefore, in the case of thetime-SLIP sequence shown in FIG. 4, BBTI is longer than TI in many cases(BBTI>TI). Then, long BBTI can be set with inhibition of unnecessarysignals in the case of applying the spatial selective 180° IR pulseafter the application of the spatial non-selective 180° IR pulse, when a180° imaging region selective IR pulse inverting the longitudinalmagnetization component Mz of the myocardium and blood in the imagingregion is applied after the application of the spatial selective 180° IRpulse for exciting the labeling region.

FIG. 5 shows another example of time-SLIP sequence set in the imagingcondition setting unit 40 shown in FIG. 3.

The abscissa axis in FIG. 5 indicates elapsing time t. In FIG. 5, ECG,RF, G, and Mz indicate R wave as ECG trigger, an RF signal, a gradientmagnetic field pulse, and a longitudinal magnetization componentrespectively. Additionally, td1 is a delay time from “the R wave time”to “the application time of the spatial non-selective 180° IR pulse”.Also, td2 is a delay time from “the R wave time just before the startingtime of the data acquisition” to “the starting time of the dataacquisition” (the same as FIG. 4).

As shown in FIG. 5, the longitudinal magnetization components of themyocardium and blood in the imaging region can be inverted again byapplying the 180° imaging region selective IR pulse, if the longitudinalmagnetization components of both myocardium and blood in the imagingregion have recovered to a positive value before the labeled blood flowsinto the imaging region. In this case, the timing, when the longitudinalmagnetization components of both myocardium and unlabeled blood becomezero simultaneously, appears. This is because the recovery rate of thelongitudinal magnetization component Mz of the myocardium is faster thanthat of the unlabeled blood.

Then, it is desirable to determine the time interval T′ from theapplication time of the 180° imaging region selective IR pulse to thestarting time of the data acquisition so that the data acquisition isstarted at the timing when the longitudinal magnetization components ofboth myocardium and unlabeled blood become zero. Thereby, signals fromthe labeled blood can be acquired with high intensity, inhibitingsignals from the myocardium and the unlabeled blood sufficiently.Furthermore, BBTI extending for 3RR, which is longer than 2RR, can beset.

Note that even if the longitudinal magnetization component Mz of theunlabeled blood has not recovered to a positive value, the longitudinalmagnetization component Mz of dominant myocardium can be inverted to anegative value by applying the 180° imaging region selective IR pulsewhen the absolute value of the longitudinal magnetization component Mzof the unlabeled blood is small enough to be ignored. Therefore, thesignal from the myocardium can be inhibited, even if BBTI is shorterthan 2RR.

Next, a setting method of the labeling region of blood will beexplained.

The labeling region can be set to a part where a coronary arteryproviding the myocardium with blood branches from an aorta. Morespecifically, as vessels providing the myocardium with blood, there arean RCA (Right Coronary Artery), an LMT (Left Main Coronary Trunk), anLCX (Left Circumflex Artery), and an LAD (Left Anterior DescendingArtery). Blood of an arbitrary vessel providing the myocardium withblood is the target for labeling.

FIG. 6 shows the first example of the labeling region (i.e., labeledregion) set in the imaging condition setting unit 40 shown in FIG. 3.

As shown in FIG. 6, the myocardium is provided with blood from the LMT,the RCA, the LCX and the LAD, each branching from the aorta. Then, asshown in FIG. 6, the slab including “the vent from the aorta to the LMT”and “the vent from the aorta to RCA” can be set as the labeling region.Moreover, by setting the imaging region to the myocardium part, imagingcan be performed with emphasized signals of the blood reaching themyocardium via the LMT or RCA after BBTI.

FIG. 7 shows the second example of the labeling region (labeled region)set in the imaging condition setting unit 40 shown in FIG. 3 and FIG. 8shows the third example of the labeling region set in the imagingcondition setting unit 40.

As shown in FIG. 7, the labeling region including only the RCA can beset by adjusting the direction of slab selection and by setting the slabfor partial excitation.

In the similar way, the labeling region can be set to the slab includingonly the LMT, as shown in FIG. 8, the range of blood provided from alabeled vessel in the myocardium can be specified by selectivelylabeling the specified vessel in the aforementioned manner. Also, thevessel providing blood to a specified region of the myocardium can bespecified. Additionally, the labeling region can be set to the slabincluding only the LCX or LAD in a similar way.

FIG. 9 shows the fourth example of the labeling region (labeled region)set in the imaging condition setting unit 40 shown in FIG. 3.

As shown in FIG. 9, if the slab on the aorta as well as the slab insidethe ventricle shown as shaded area are set as labeling regions, it ispossible to label blood. Thereby, the volume of the labeled blood can bemaintained, and the labeled blood can be provided inside the myocardiumfor a longer time. A slab inside the ventricle can be excitedselectively by using “2D (two-dimensional) localized excitation” or “thecombination of 2D localized excitation and 3D slab excitation”.

FIG. 10 shows the fifth example of the labeling region (labeled region)set in the imaging condition setting unit 40 shown in FIG. 3, and FIG.11 shows the sixth example of the labeling region (labeled region) setin the imaging condition setting unit 40 shown in FIG. 3.

As shown in FIG. 10, the labeling region can be set by using “a3-chamber view image (In and Out Flow View) in the cross-sectiondisplaying 3 chambers of a right ventricle, a left ventricle and a leftatrium” as a scout image (positioning image). In this case, the labelingregion can be set easily and accurately to a slab including the vent ofthe coronary artery in the cardiac basal side.

Here, if the width of the labeling region is narrow, the reachingdistance of the labeled blood becomes shorter according to the decreasedamount of the labeled blood and consequently the labeled blood does notreach with enough quantity in some cases.

Then, as shown in FIG. 11, (the width of) the labeling region (labeledregion) can be set wider but exclusive of the imaging region in the3-chamber view image. In this case, it is possible to set a longer BBTI,because the reaching distance of the labeled blood becomes longer.

The 3-chamber view image can be acquired by using a known technology.Concretely speaking, the 3-chamber view image can be acquired, e.g., byrepeating “acquisition of a scout image on a linear ROI (region ofinterest)” and “setting of a linear ROI in the acquired scout image”.For example, a 2D SSFP sequence can be used for acquiring the 3-chamberview image.

FIG. 12 shows the seventh example of the labeling region (labeledregion) set in the imaging condition setting unit 40 shown in FIG. 3. Asshown in FIG. 12, the labeling region can be set with display of “a3D-MRA image including the coronary artery in parallel with an objectand a cardiac sagittal plane” as a scout image. Also in this case, thelabeling region can be set easily and precisely to a slab inclusive ofthe vent of the coronary artery, because branching behavior of thecoronary artery is visible.

3D-MRA image data of the coronary artery can be acquired in a shorterperiod, if the 3D-MRA image data are set as image data of thickness Th1which is thin enough to be acquired during breath hold. On the contrary,a scout image of wider range for setting the labeling region can beacquired, if the 3D-MRA image data of the coronary artery are acquiredunder natural respiration with the aforementioned correction inhibitingthe influence of motion caused by respiration.

As shown in FIG. 12, the labeling region can be set, e.g., as “a regionhaving infinite thickness” or “a slab having finite thickness Th2 on the3D-MRA image displayed sterically”. Alternatively, the labeling regioncan be set as “a region having infinite thickness” or “a slab havingfinite thickness on projection image data such as MIP (maximum intensityprojection) image data acquired from the 3D-MRA image data”. Moreover,as another example, the labeling region can be set on 2D-MRA image datain an appropriate cross-section acquired from the 3D-MRA image data.

Although FIG. 4 shows an example of imaging by using a Flow-Out methodof the time-SLIP method, imaging can be performed by using a Flow-Inmethod and an On-Off Alternative difference method.

The Flow-Out method is a method of inhibiting signals of myocardium byapplying a spatial non-selective 180° IR pulse as shown in FIG. 4, whileacquiring imaging data at the same timing as blood labeled by thespatial selective 180° IR pulse in the labeling region near a coronaryartery is perfused into the myocardium. Note that in the Flow-Outmethod, the spatial non-selective 180° IR pulse can be set OFF.

The Flow-In method is a method of applying only the spatial selective180° IR pulse(s) to an imaging region including myocardium with thespatial non-selective 180° IR pulse set OFF. In this method, imaging canbe performed so that blood flowing into the imaging region after theapplication of the spatial selective 180° IR pulse is distinguished fromother parts of excited state. This is because the blood flowing into theimaging region after the application of the spatial selective 180° IRpulse is not influenced by the spatial selective 180° IR pulse (is in anunexcited state).

The On-Off Alternative difference method is a method of generatingdifference image data between an On image and an Off image as blood flowimage data. The On image is an image whose image data are acquired atthe timing when blood labeled by a spatial selective 180° IR pulse inthe labeling region near a coronary artery flows into myocardium, in away similar to the Flow-Out method. The Off image is an image whoseimage data are acquired without applying the spatial selective 180° IRpulse (with other imaging conditions set the same as the On image). Inthe On-Off Alternative difference method, signals from labeled blood canbe extracted selectively and blood flow image data can be generated byusing the extracted blood signals.

Note that it is more desirable to perform data acquisition of On imagesand data acquisition of Off images alternately than to perform dataacquisition of all the Off images after finishing data acquisition ofall the On images needed for generating blood flow image data. This isbecause interval of imaging time between each On image and each Offimage is shorter in the former, and influence of motion of an object(motion artifact) is smaller in the former.

Imaging conditions for acquiring blood flow image data corresponding toa plurality of BBTIs respectively are set in the imaging conditionsetting unit 40 by changing BBTI in the time-SLIP method. That is, aplurality of mutually different BBTIs is set as imaging conditions inthe imaging condition setting unit 40.

Additionally, the delay time td1 and td2 of a pulse sequence based on anappropriate R wave are set in the imaging condition setting unit 40, sothat data acquisition timing is in the same cardiac time phase or incloser cardiac time phase between different BBTIs, as mentioned above.Although the setting of these delay time td1 and td2 can be performedautomatically in the imaging condition setting unit 40, it can be setmanually by inputting necessary information to the imaging conditionsetting unit 40 through the input device 33.

Although the delay time td1 of a pulse sequence may be set to a timeinterval from the timing of an R wave to the application timing of thespatial non-selective 180° IR pulse as shown in FIGS. 4 and 5, the delaytime td1 may be set by using another criterion of the pulse sequence.Moreover, a time condition influencing other data acquisition timing maybe adjusted as a delay time of a pulse sequence instead of the delaytime td1 from an R wave. For example, a time interval from the timing ofan R wave to the application timing of spatial selective 180° IR pulse(td1+ΔT in FIG. 4) can be set as a delay time. In this case, anappropriate delay time can be determined automatically or manuallyaccording to BBTI.

For example, when the first BBTI is 1200 ms (millisecond) and the delaytime (td1+ΔT) from the timing of R wave to the application timing ofspatial selective 180° IR pulse is 400 ms, start timing of dataacquisition is 1600 ms after the timing of the R wave. Thus, when thesecond BBTI is 1400 ms, the start timing of the data acquisition can beset in the same cardiac time phase by setting “the delay time (td1+ΔT)from the timing of the R wave to the application timing of the spatialselective 180° IR pulse” to 200 ms.

According to the above calculation method, imaging conditions of eachsequence such as the delay time td1 can be calculated automatically sothat the cardiac time phase of the start timing of the data acquisitionaccords through respective sequences having mutually different BBTIs.This automatic calculation may be performed according to (A) “values oftime parameters such as BBTI and TI in the sequence whose BBTI value isselected as a reference value (criterion)” and (B) “a priority conditionas to which time parameter such as ΔT is preferentially used todetermine imaging conditions of other sequences (sequences whose BBTIvalues are not the reference value)”. Thereby, values of each timeparameter of sequences corresponding to other BBTI can be setautomatically by setting only (A) “values of each time parameters in thesequence whose BBTI value is selected as criterion” and (B) theaforementioned priority condition. According to the above automaticsetting method, the number of imaging conditions a user should set isrequired less, and this leads to improvement of operability of an MRIapparatus.

In the Flow-Out method and the On-Off Alternative difference method,BBTI corresponds to traveling time of labeled blood. Additionally, BBTIcorresponds to traveling time of unexcited blood in the Flow-In method.That is, BBTI corresponds to traveling time of blood flowing into animaging region. Thus, if imaging is performed with different BBTIs, aplurality of blood flow image data having mutually different reachingpositions of blood respectively can be acquired. For example, BBTI isset to 600 ms, 800 ms, 1000 ms and 1200 ms.

Next, setting method of TI and BBTI will be explained.

The imaging parameter determining unit 40B has a function of setting TIand BBTIs. TI and BBTIs can be set individually and can be determined bya prescan respectively. Note that the “prescan” and “prep scan”discussed later mean operation from pulse application such as a sliceselective pulse necessary for data acquisition to completion ofgeneration of image data by using image reconstruction processing.

The prescan condition setting unit 40A has a function of setting imagingconditions of a TI-prep scan which is a prescan for determining TI andhas a function of setting imaging conditions of BBTI-prep scan which isa prescan for determining BBTIs.

FIG. 13 is a chart explaining determination method of TI and BBTIs setas imaging conditions in the imaging condition setting unit 40 shown inFIG. 3.

In FIG. 13, the abscissa axis indicates elapsing time t. As shown inFIG. 13(A), imaging conditions of the TI-prep scan performing dataacquisition plural times with mutually different TI (TI1, TI2, TI3, . .. , TIn) are set (note that “n” represents the number of TIs). Anarbitrary sequence, which can be used for an imaging sequence such asthe FASE sequence, can be used for the data acquisition sequence of theTI-prep scan. Note that it is desirable to use the same sequence as theimaging sequence for the data acquisition of the TI-prep scan.Additionally, it is desirable to use a 2D sequence for the dataacquisition of the TI-prep scan in order to shorten time needed for thedata acquisition.

As shown in FIG. 13(B), blood flow cross-sectional images are generatedby performing the TI-prep scan, and thereby blood flow cross-sectionalimages I(TI1), I(TI2), I(TI3), . . . , I(TIn) are acquired. Then, anappropriate TI (TIopt) can be determined by selecting the blood flowcross-sectional image (corresponding to TIopt) with the best contrastout of the plurality of blood flow cross-sectional images I(TI1),I(TI2), I(TI3), . . . , I(TIn). That is, information on determination ofTI value can be inputted into the imaging parameter determining unit 40Bthrough the input device 33 as selection information on blood flowcross-sectional images.

Note that the imaging parameter determining unit 40B may be providedwith a function of automatically selecting the blood flowcross-sectional image with good contrast by using data processing suchas threshold processing.

In the similar way, imaging conditions of a BBTI-prep scan performingdata acquisition plural times with mutually different BBTIs (BBTI1,BBTI2, BBTI3, . . . , BBTIm) are set as shown in FIG. 13(C) (note that“m” represents the number of BBTIs). An arbitrary sequence, which can beused for an imaging sequence such as the FASE sequence, can be used forthe data acquisition sequence of the BBTI-prep scan. Note that it isdesirable to use the same sequence as the imaging sequence for the dataacquisition of the BBTI-prep scan. Additionally, it is desirable to usea 2D sequence for the data acquisition of the BBTI-prep scan in order toshorten time needed for the data acquisition.

As shown in FIG. 13(D), blood flow cross-sectional images are generatedby performing the BBTI-prep scan, and thereby blood flow cross-sectionalimages I(BBTI1), I(BBTI2), I(BBTI3), . . . , I(BBTIm) are acquired.Then, out of the plurality of blood flow cross-sectional imagesI(BBTI1), I(BBTI2), I(BBTI3), . . . , I(BBTIm), a range of blood flowcross-sectional images I(BBTIst), . . . , I(BBTIend), in which travelingdistance of blood flowing into the imaging region is in appropriaterange, are selected. By this selection, an appropriate range of BBTIs(from BBTIst to BBTIend) are determined. That is, “plural BBTI values asselection information on blood flow cross-sectional images” or“determination information on default, final value and changing amountof BBTI” can be inputted into the imaging parameter determining unit 40Bthrough the input device 33.

For example, by performing 2-dimensional imaging with plural BBTIsranging from 100 ms to 2000 ms with increment of 100 ms, BBTIs rangingfrom 600 ms to 1200 ms with increment of 200 ms may be determined forimaging. By this way, changing amount of BBTI values for imaging may bechanged from that of the BBTI-prep scan.

It is desirable to set imaging cross-sections of the BBTI-prep scan to“an arbitrary plane inclusive of the cardiac long axis” or “a pluralityof long axial planes rotated around the cardiac long axis”. This is sothat the myocardial cross-sectional position in the cardiac long axialdirection, where the blood labeled according to BBTI reaches, is visibleon the BBTI-prep image.

That is, in terms of determining appropriate BBTI and its variationrange, it is desirable to set the BBTI-prep images to the same images asscout images for setting the labeling region or 2D images in parallelwith these scout images.

Then, 3D imaging can be performed using appropriate TI (TIopt) and aplurality of BBTIs (BBTIst, . . . , BBTIend) as imaging conditions asshown in FIG. 13(E).

An appropriate TI value and a plurality of appropriate BBTIs aredifferent according to conditions such as age, sexuality, body heightand body weight of an object, stage of progression in a lesion area andan imaging region. Then, a database of an appropriate TI value and aplurality of appropriate BBTIs can be empirically compiled per each ofthe those conditions. That is, a table data (table-type database)indicative of an appropriate TI value and a plurality of appropriateBBTIs per each of the conditions of an object can be stored in theimaging parameter storing unit 40C.

In this case, when information on the conditions of an object isinputted to the imaging parameter determining unit 40B by operatinginput device 33, the imaging parameter determining unit 40B can refer tothe table data on the imaging parameter storing unit 40C and can obtainan appropriate TI value and/or a plurality of appropriate BBTIscorresponding to the inputted conditions. In this manner, an appropriateTI value and/or a plurality of appropriate BBTIs corresponding toconditions of an object can be determined without performing the TI-prepscan and/or the BBTI-prep scan.

Next, other functions of the computer 32 will be explained.

The sequence controller control unit 41 has a function of acquiringimaging conditions including pulse sequences from the imaging conditionsetting unit 40 based on command information on start of imaging, andperforming drive control of the sequence controller 31 by inputting theacquired imaging conditions to the sequence controller 31. Additionally,the sequence controller control unit 41 has a function of receiving rawdata from the sequence controller 31 and arranging the raw data ink-space formed in the k-space database 42.

The blood flow image generating unit 43 has a function of obtainingk-space data from the k-space database 42, and generating a plurality ofblood flow image data corresponding to mutually different BBTIs byperforming image reconstruction processing including FT (Fouriertransformation) and necessary image processing. Additionally, the bloodflow image generating unit 43 has a function of writing the generatedblood flow image data onto the image database 44.

For example, in the case of the On-Off Alternative difference method,the blood flow image generating unit 43 performs image processing ofdifference data between “On image data acquired by performing labelingwith the spatial selective 180° IR pulse” and “Off image data acquiredwithout performing labeling”.

Moreover, in the case of correcting respiratory motion by using the RMCmethod, the blood flow image generating unit 43 performs phasecorrection of the k-space data with shift amount corresponding to amountof respiratory motion and positional correction of blood flow image dataso as to remove the influence of respiratory motion. The amount ofrespiratory motion can be determined, for example, as amount ofvariation from a reference value of real space data obtained byperforming FT on the k-space data such as the MPP acquired for detectingrespiratory level.

Moreover, the blood flow image generating unit 43 has a function ofperforming correction processing. In this correction processing, signalcomponents of telae is removed from “image data obtained by performingimage reconstruction processing on the k-space data” and only the bloodflow signal components are extracted as the blood flow image data.

FIG. 14 is an explanatory chart showing the generation processing of theblood flow image data performed by the blood flow image generating unit43. In the generation processing, signal components except blood isremoved from image data.

In each of FIGS. 14(A) and 14(B), the abscissa axis indicates timelength of BBTI (second) and the vertical axis indicates signal intensityS. In FIG. 14(A), signal values of image data are plotted per BBTI. Asshown in FIG. 14(A), the longer BBTI is, the stronger the signalintensity S of the image data becomes. This is because the longitudinalmagnetization components of telae (tissues) and unlabeled blood recoveraccording to the length of BBTI. That is, the longer BBTI is, the moresignal component from the background is superimposed and this changesthe base line of the blood signal. Thus, in order to determine signalintensity of the blood flow image data more accurately, it is desirableto perform base line correction in which signal components from thelabeled blood are extracted by removing signal components of thebackground from the image data.

Therefore, the blood flow image generating unit 43 has a function ofgenerating the blood flow image data as shown in FIG. 14(B) byperforming the aforementioned base line correction on image data. Thebase line correction can be performed by subtracting the backgroundcomponent except labeled blood from the image data. Note that the baseline correction may be performed on the k-space data before the imagereconstruction processing instead of the image data alternatively.Signal values of the background components can be determined by imagingor by performing simulation of a Ti recovery curve of longitudinalmagnetization component Mz.

As the imaging for determining the signal value of the backgroundcomponent, for example, there is a method of applying a spatialnon-selective 180° IR pulse to invert the longitudinal magnetizationcomponent Mz of the background part without applying a spatial selective180° IR pulse for labeling blood. Alternatively, the signal value of thebackground component can be acquired by imaging in which the labelingregion is set as a region whose labeled blood does not flow into theimaging region at the timing of data acquisition. Additionally, if thesignal value of the background component is acquired by imaging for onlya part of the imaging region that needs the base line correction,imaging time and data processing amount are decreased.

The blood flow information generating unit 45 has a function of (A)obtaining a plurality of blood flow image data corresponding to mutuallydifferent BBTIs respectively from the image database 44, (B) performingcardiac function analysis based on the plurality of blood flow imagedata, (C) generating blood flow information indicating cardiac functionin myocardium in an arbitrary description method as the result of thecardiac function analysis, and (D) displaying the blood flow informationon the display device 34.

As an example of display of the blood flow information, there is amethod of performing parallel display of the plurality of blood flowimages corresponding to mutually different BBTIs respectively. Then, thelonger BBTI a blood flow image corresponds to, the longer distance theblood flow image indicates as traveling distance of the emphasized bloodflowing into the imaging region. This is because BBTI corresponds tosupply time of blood to the imaging region. That is, a plurality ofblood flow images indicating respectively different traveling distancesof blood can be displayed corresponding to each BBTI.

Moreover, blood flow image data having a time axis can be generated asthe blood flow information like cine image data for consecutivelydisplaying blood flow images on an image to image basis in the order ofBBTI values. In this case, the blood flow images can be displayed sothat the behavior of blood flow gradually flowing inside the myocardiumis shown.

Additionally, a profile of the blood flow image data per BBTI at anarbitrary myocardial cross-sectional position can be generated as theblood flow information.

FIG. 15 is a diagram showing an example of a profile of the blood flowimage data generated by the blood flow information generating unit inFIG. 3. FIG. 15(A) shows a cross-sectional image including themyocardial short axis. FIG. 15(B) shows the profile of the blood flowimage data on a linear ROI (region of interest) set on thecross-sectional image including the myocardial short axis shown in FIG.15(A). That is, the abscissa axis in FIG. 15(B) shows cross-sectionalpositions on the myocardial short axis and the vertical axis in FIG.15(B) shows signal intensity of the blood flow image data.

As shown in FIG. 15(B), the myocardium is covered with its endocardium(endomembrane) and epimyocardium (epicardium), and the left ventricle isformed inside the myocardium. Additionally, the left ventricle isadjacent to the right ventricle. By generating a profile in thedirection of the short axis in such myocardial cross-section, the datashown in FIG. 15(B) are obtained. Because blood flow amount inside themyocardium is small compared with the inside of the left and rightventricles, the blood signal intensity inside the myocardium isrelatively small as shown in FIG. 15(B). A profile like FIG. 15(B) canbe made per BBTI.

FIG. 16 is a diagram showing an example of a set of profiles of theblood flow image data corresponding to a plurality of different BBTIs.Note that these profiles are made by the blood flow informationgenerating unit in FIG. 3. In FIG. 16, each vertical axis shows bloodsignal intensity and each abscissa axis shows positions in the directionof the myocardial short axis.

For example, as shown in FIGS. 16(A), 16(B), 16(C) and 16(D), profilesof the respective blood flow image data in the case of changing BBTIsuch as 600 ms, 800 ms, 1000 ms and 1200 ms can be made. Then, bydisplaying the respective profiles of the blood flow image datacorresponding to a plurality of different BBTIs for an arbitrarymyocardial cross-section in parallel, these profiles can be comparedwith each other.

Blood, which has flowed into the imaging region, flows into the insideof the myocardium from the epimyocardium and flows into the inside ofthe left ventricle from the endocardium. Thus, after the signalintensity near the epimyocardium has gradually increased according tothe extension of the BBTI, the signal intensity near the endocardiumincreases due to the movement of blood toward the endocardium side asshown in FIGS. 16(A), 16(B), 16(C) and 16(D). By this way, the travelingbehavior of the blood in the myocardium according to change in BBTI canbe observed as time change of signal intensity in the myocardium.Additionally, distribution of blood signal can be analyzed.

These profiles of the blood flow image data can be made and displayed3-dimensionally, instead of being made as an arbitrary cross-section. Inother words, a profile comprising 3 parameters, which are respectivevalues in the 2 directions crossing on a myocardial cross-section (e.g.,x coordinate value and y coordinate value) and signal value S, can bedisplayed as a oblique perspective figure in torus-shape (doughnutshape). Thereby a part with relatively low signal intensity can beeasily found out.

Additionally, by performing sign inversion processing on the blood flowimage data, highlight display can be performed in the way the lowersignal intensity a part has, the higher brightness the part is displayedwith. Then, even if the low signal intensity part such as an infarctionpart is localized, it can be easily discovered. Moreover, if the profileis displayed 3-dimensionally, a low signal intensity part can beobserved as a peak.

Additionally, when the blood flow image generating unit 43 does notperform the aforementioned base line correction, it means that thebackground signal component is superimposed on the obtained profile.Then, the obtained profile can be displayed with different colors and adisplay method so that the respective signal components of thebackground and the labeled inflowing blood are distinguishable from eachother.

Moreover, by calculating signal difference between a plurality of bloodflow image data corresponding to different BBTIs respectively as theblood flow information, a lesion area such as an infarction area and anischemia area in the myocardium can be specified based on the calculatedsignal difference.

FIG. 17 is a diagram showing an example of distinguishably displayedlesion areas of the myocardium identified by the blood flow informationgenerating unit in FIG. 3 based on signal difference between blood flowimage data corresponding to different BBTIs. FIG. 17 is a blood flowinformation image per segment displaying signal (signal intensity)difference between the blood flow image data corresponding to differentBBTIs by dividing a short axial cross-section of the myocardium into aplurality of segments. That is, luminance display of the signaldifference between the blood flow image data corresponding to differentBBTIs is possible with high resolution as shown in FIG. 17, because theblood flow image data are acquired without using a contrast medium.Color display per segment with at least one of chromatic colorsaccording to signal values is possible with regard to the signaldifference.

In this case, the signal difference between 3-dimensional blood flowimage data can be calculated on a pixel to pixel basis. Thereby, theblood flow information can be acquired with higher precision. In thecase of calculating the difference values per pixel, each representativevalue such as an average value in each segment may be displayed.

Note that the signal differences between the blood flow image data maybe displayed as bull's-eye display in which data of a plurality ofmutually different myocardial cross-sections are displayed as oneconcentric image. Additionally, signal values of the blood flow imagedata can be displayed per segment.

For example, the delta (difference) between reference data and the bloodflow image data corresponding to each BBTI can be calculated. In thiscase, the reference data are the data acquired without applying aspatial selective 180° IR pulse (i.e., acquired with BBTI set to zero).Then, the signal difference value according to traveling distance ofblood at each data acquisition time can be obtained.

The signal difference value in a normal area is equal to or more than aconstant value, because the amount of supplied blood is sufficientthere. However, the signal difference value in an infarction area whereblood is not supplied is zero, because blood signal does not changethere. Additionally, the signal difference value in an ischemia area,where the amount of supplied blood is small, is low. This is becausevariation of blood signal is small there.

Thus, range of an infarction area can be detected by judging whether ornot the signal difference value can be regarded as zero at each positionand by specifying the region where the signal difference is value can beregarded as zero. Additionally, range of an ischemia area can bedetected by judging whether or not the signal difference value can beregarded as equal to or less than a threshold value corresponding to anischemia part at each position and by specifying the region where thesignal difference value can be regarded as equal to or less than thethreshold value. A lesion area such as an infarction area and anischemia area can be distinguishably (identifiably) displayed by using,e.g., different patterns as shown in “the color 1 part” and “the color 2part” in FIG. 17. Although FIG. 17 is drawn in grayscale for reasons ofexpediency, “the color 1 part” and “the color 2 part” in FIG. 17 may becolored with different chromatic colors respectively so that they aredistinguishably displayed as lesion areas.

FIG. 18 is a diagram showing the signal difference in the line ROI-Acrossing the ischemia area shown in FIG. 17. FIG. 19 is a diagramshowing the signal difference in the line ROI-B crossing the infarctionarea shown in FIG. 17.

In FIG. 18 and FIG. 19, each vertical axis indicates signal differencevalues ΔS between the blood flow image data corresponding to differentBBTIs and each abscissa axis indicates positions on the linear ROI. Asshown in FIG. 18, the signal difference value ΔS in the ischemia area(shown as “SLIGHT VARIATION”) is small in the profile of the signaldifference value on the linear ROI A in FIG. 17 crossing the ischemiaarea. Additionally, as shown in FIG. 19, the signal difference value ΔSin the infarction area (shown as “NO VARIATION”) is zero in the profileof the signal difference value on the linear ROI B in FIG. 17 crossingthe infarction area. Moreover, these curves of the signal differencevalues can be displayed as the blood flow information.

FIG. 20 is an example showing how the blood flow information generatingunit in FIG. 3 enables users to select the display of each signaldifference value between the blood flow image data corresponding todifferent BBTIs in a plurality of linear ROIs on a cross-section of themyocardium.

FIG. 20 is a blood flow information image per segment displaying signaldifference between the blood flow image data corresponding to differentBBTIs by dividing a short axial cross-section of the myocardium intoplural segments. As shown in FIG. 20, a plurality of linear ROIs (ROI-1,ROI-2, ROI-3, . . . ) can be selectively set on a blood flow informationimage. Then, if an arbitrary linear ROI is selected through the inputdevice 33 by operation of, e.g., a mouse, the curve of the signaldifference value ΔS on the selected linear ROI is displayed like FIGS.18 and 19.

Note that a plurality of linear ROIs may be displayed as bulls-eyedisplay. Additionally, the computer 32 may be configured to display aprofile of signal values on the selected linear ROI by displaying signalvalues of the blood flow image data per segment, when an arbitrarylinear ROI is selected out of a plurality of linear ROIs. Moreover,3-dimensional display, sign inversion display, and distinguishabledisplay of background component are possible with regard to a profile ofthe signal difference value ΔS in a way similar to the profile of signalintensity.

In addition, when the signal difference between the blood flow imagedata corresponding to different BBTIs is calculated, it is importantthat each of the blood flow image data for the calculation targetindicates “the position of the myocardial cross-section” correspondingto the positions of the other blood flow image data. Then, as mentionedabove, it is desirable to perform the positional correction of the bloodflow image data so that (A) the cardiac time phase at the dataacquisition timing accords with each other through the blood flow imagedata which are the calculation target of the difference value and (B)each position of the myocardial cross-section on the blood flow imagedata accords with each other. This is because the blood flow informationcan be acquired more precisely in that manner. The positional correctionof the blood flow image data can be performed in the blood flowinformation generating unit 45.

FIG. 21 is a diagram showing reference positions for the blood flowinformation generating unit 45 in FIG. 3 to perform the positionalcorrection between the blood flow image data.

As shown in FIG. 21, the myocardium is covered with the endocardium(endomembrane) and the epimyocardium, and the left ventricle is formedinside the myocardium. Additionally, the left ventricle is adjacent tothe right ventricle. On such a myocardial short axial cross-sectionalimage, the blood flow information such as the signal difference valuecan be acquired more accurately by setting one or plural referenceposition(s) at the border part between the left and right ventricles andby performing the positional correction such as parallel shift orrotational locomotion of the respective blood flow image data in thefollowing manner. That is, the positional correction should be performedso that the reference positions more accord with each other through theblood flow image data corresponding to different BBTIs. Note thatalthough the positional correction can be performed more easily in thecase of setting 2 reference positions as shown in FIG. 21, thepositional correction can be performed in the case of setting only onereference position.

(Operation and Action)

Next, the operation and action of the magnetic resonance apparatus 20will be explained.

FIG. 22 is a flowchart showing a procedure for acquiring the blood flowinformation on cross-sections of the myocardium of the object P anddisplaying their images by performing a non-contrast MRA imaging withthe magnetic resonance imaging apparatus 20 shown in FIG. 2.Hereinafter, the case of performing imaging operation under the Flow-Outmethod of the time-SLIP method will be explained as an example.

First, the object P is set on the bed 37 in advance. Then, a staticmagnetic field is formed in the imaging region inside the staticmagnetic field magnet 21 (superconducting magnet) excited by the staticmagnetic field power supply 26. Additionally, electric current issupplied from the shim coil power supply 28 to the shim coil 22, therebythe static magnetic field formed in the imaging region is uniformed.

Next, in step 1, the imaging parameter determining unit 40B determinesTI and a plurality of mutually different BBTIs of the time-SLIPsequence. These TI and BBTIs can be determined by performing a prescanor searching the database stored in the imaging parameter storing unit40C.

In the case of determining TI and/or BBTIs by performing the prescan,the imaging conditions for the prescan are set in the imaging conditionsetting unit 40 in the way explained with FIG. 13. Then, the prescan isperformed under ECG synchronization according to the imaging conditionsset for the prescan. Moreover, TI and/or BBTIs are (is) determined basedon the acquired blood flow images in the prescan. Additionally, in thecase of determining TI and/or BBTIs by searching the database, theimaging parameter determining unit 40B obtains “TI and/or BBTIscorresponding to conditions inputted through the input device 33” fromthe imaging parameter storing unit 40C.

Next, in step 2, the time-SLIP sequence with the determined TI and theplurality of different BBTIs (see FIGS. 4 and 5) are set as imagingconditions for imaging in the imaging condition setting unit 40. Then,imaging without using a contrast medium is performed in synchronizationwith an ECG signal from the ECG unit 38 according to the set imagingconditions.

Concretely speaking, when imaging start command is inputted from to theinput device 33 to the sequence controller control unit 41, the sequencecontroller control unit 41 inputs the imaging conditions including thepulse sequence obtained from the imaging condition setting unit 40 tothe sequence controller 31. The sequence controller 31 drives thegradient magnetic field power supply 27, the transmitter 29 and thereceiver 30 in synchronization with the ECG signal from the ECG unit 38according to the set pulse sequence so that a gradient magnetic field isformed in the imaging region where the object P is set and the RF coil24 generates RF signals.

Therefore, NMR signals generated by nuclear magnetic resonance insidethe object P are detected by the RF coil 24 and inputted to the receiver30. The receiver 30 receives the NMR signals from the RF coil 24 andgenerates raw data. The receiver 30 inputs the generated raw data to thesequence controller 31. The sequence controller 31 inputs the raw datato the sequence controller control unit 41, and the sequence controllercontrol unit 41 arranges the raw data in the k-space formed in thek-space database 42 as k-space data.

Note that the RMC is performed, if necessary, and data acquisitionregion is corrected according to the respiratory motion amount acquiredbased on the MPP.

Next, in step 3, the blood flow image generating unit 43 generates aplurality of image data corresponding to different BBTIs by obtainingthe k-space data from the k-space database 42 and performing imagereconstruction processing on the k-space data. Additionally, in the caseof performing the RMC, phase of the k-space data or a position of theimage data is corrected according to the respiratory motion amountacquired based on the MPP, if necessary.

Next, in step 4, the blood flow image generating unit 43 generates theplurality of blood flow image data corresponding to different BBTIs byperforming necessary image processing such as differential processing onthe reconstructed image data. The generated blood flow image data arestored in the image database 44. Moreover, the blood flow imagegenerating unit 43 performs the base line correction on the image dataso as to remove signal components of Ti recovery (longitudinalrelaxation) of the background, if necessary. Note that the base linecorrection may be performed on the k-space data on which the imagereconstruction processing has not been performed yet.

Next, in step 5, the blood flow information generating unit 45 generatesthe blood flow information on myocardial cross-sections based on theplurality of blood flow image data corresponding to different BBTIs anddisplay the generated blood flow information on the display device 34.For example, a plurality of blood flow images corresponding to differentBBTIs, profiles of signal intensity in myocardial cross-sections asshown in FIG. 16, a segment image of a myocardial cross-sectionindicating signal difference values corresponding to different BBTIs asshown in FIG. 17, and a curve of signal difference values as shown inFIG. 18 or 19 are displayed on the display device 34 as the blood flowinformation. Additionally, the positional correction of the blood flowimage data is performed by using at least one of reference positions setto the border of the left and right ventricles as shown in FIG. 21, ifnecessary.

Therefore, a user can easily discover a lesion area such as aninfarction area and an ischemia area, and can understand the range ofthe lesion area.

The magnetic resonance imaging apparatus 20 configured as mentionedabove can acquire the blood flow information in a myocardium partwithout using a contrast medium in a cardiac study for an infarctionpart and an ischemia part. Specifically, the magnetic resonance imagingapparatus 20 performs spatial selective excitation so that signals ofblood flowing into the imaging region set to myocardium part isdistinguishable. In addition, the magnetic resonance imaging apparatus20 changes the time from the region selective excitation to dataacquisition. Thereby, the magnetic resonance imaging apparatus 20generates a plurality of blood flow images indicating mutually differentinflowing distance of blood.

Moreover, the magnetic resonance imaging apparatus 20 calculates theblood flow information such as a profile of the blood signal intensityand the blood signal difference values in a myocardial cross-sectionbased on the plurality of blood flow image data indicating mutuallydifferent traveling distance of blood, and displays the blood flowinformation. Thereby, an infarction area and an ischemia area can bespecified.

(Effect)

Therefore, according to the magnetic resonance imaging apparatus 20,there is no necessity of using a gadolinium contrast agent, and imagingcan be performed with high resolution because there is no limit of dataacquisition time. Concretely speaking, the magnetic resonance imagingapparatus 20 has several-fold in-plane resolution as compared withscintigraphy and perfusion examination in the conventional MRI. This isbecause the magnetic resonance imaging apparatus 20 performs3-dimensional imaging. Therefore, resolution of a profile of bloodsignal improves and an infarction part and an ischemia part inmyocardium can be depicted with high resolution.

Additionally, the magnetic resonance imaging apparatus 20 can depictnatural flow of blood by a labeling method such as the time-SLIP method.Therefore, a blood flow image at an arbitrary time and a map of bloodsignal can be acquired. Moreover, the magnetic resonance imagingapparatus 20 can detect a lesion area such as an infarction part and anischemia part based on time variation of blood signal and information onwhether or not blood has moved on a blood flow image. In this case, therange of the lesion area can be distinguishably displayed with at leastone of chromatic colors.

Moreover, there is no need to apply stress such as medication stress andexercise stress in the exemplary embodiments.

Additionally, micro-vascularity can be obtained by setting BBTI of thetime-SLIP method, e.g., to 300 ms, 500 ms, 800 ms and 1000 ms. Then, themicro-vascularity can be observed by displaying profiles of blood signalor by displaying blood signal difference with bulls-eye display.

Additionally, the magnetic resonance imaging apparatus 20 can be usedfor screening study in comprehensive medical examination, because it canperform ischemia examination in myocardium without using a contrastmedium.

(Modifications) 1. First Modification

In the aforementioned embodiment, an example of applying spatialselective 180° IR pulses as spatial selective excitation pulses fordistinguishing signal of blood flowing into the imaging region isexplained. However, the exemplary embodiments are not limited to suchconfiguration. A 90° saturation pulse can be used as the spatialselective excitation pulse. When a 90° saturation pulse is applied asthe spatial selective excitation pulse, a time interval from applicationtiming of the 90° saturation pulse to start timing of data acquisitionis set to a different value from the time interval in the case ofapplying the first and second spatial selective 180° IR pulse as thespatial selective excitation pulses (refer to FIGS. 4 and 5). Forexample, blood of unsaturated state flowing from the outside of theimaging region into the imaging region can be selectively emphasized,when imaging is performed under the following two conditions. That is,(A) the imaging region should be set to the entire myocardium and (B)the 90° saturation pulse should be applied to the same region as theimaging region with a changed time interval from the start timing of thedata acquisition.

Additionally, for example, the data acquisition may be performed afterapplying the 90° saturation pulse as notched pulse without applying aspatial non-selective 180° IR pulse. That is, the 90° saturation pulseis applied as the notched pulse to the cardiac region exclusive of onlythe aorta (e.g., the region exclusive of only the “LABELED REGION” inFIG. 6 or 9). In this case, the signal level of the background can beinhibited, because the longitudinal magnetization component Mz of bloodbecomes zero in the region to which the notched pulse is applied. At thesame time, the blood in the aorta without the influence of the notchedpulse can be distinguished by performing data acquisition at anappropriate timing. This is because the longitudinal magnetizationcomponent Mz of the blood in the aorta without the influence of thenotched pulse is one which is the same as the direction of the staticmagnetic field, and it inflows with high signal level into the imagingregion.

2. Second Modification

In the aforementioned embodiment, an example of imaging underapplication of neither medicational stress nor exercise stress isexplained. However, the exemplary embodiments are not limited to suchconfiguration. Imaging may be performed applying both medication stressand exercise stress. Moreover, by performing the following two imagingsequences (X) and (Y) respectively, acquired blood flow images may bedisplayed in parallel so that blood flow images acquired in the imagingsequences (X) and (Y) can be compared with each other. In this case,both medicational stress and exercise stress or either one of them are(is) applied in the imaging sequence (X), whereas neither medicationalstress or exercise stress is applied in the imaging sequence (Y).Additionally, blood flow image data for diagnosis can be generated andtheir images can be displayed by performing differential processingbetween “the blood flow image data acquired under application of stressto an object” and “the blood flow image data acquired without applyingany stress to the object”. By performing such comparative display anddifferential display, a patient is diagnosed more precisely.

3. Other Modification

In the aforementioned embodiment, an example of a setting pulse sequenceby using an R wave of an ECG signal as a synchronization signal isexplained with FIGS. 4 and 5. However, the exemplary embodiments are notlimited to such configuration. The aforementioned PPG (peripheral pulsegating) signal or a cardiac sound synchronization signal may be acquiredso that a pulse sequence is appropriately set based on the acquiredsignal.

Although an example of setting the imaging region to a heart isexplained in the aforementioned embodiment, the blood flow image datacan be acquired by setting the imaging region to a head or another organexcept a heart, such as a kidney and a liver.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the exemplary embodiments. Indeed, the novel methods andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the exemplary embodiments. The accompanying claimsand their equivalents are intended to cover such forms or modificationsas would fall within the scope and spirit of the exemplary embodiments.

What is claimed is:
 1. A magnetic resonance imaging apparatuscomprising: an imaging data acquiring unit which acquires a plurality of3-dimensional imaging data each corresponding to mutually differenttraveling time of inflowing blood flowing into an imaging regionincluding myocardium in synchronization with a heartbeat withoutadministration of a contrast medium, by applying a spatial selectiveexcitation pulse plural times for distinguishably displaying theinflowing blood and by changing a time interval from application timingof the spatial selective excitation pulse to acquisition timing of theimaging data; a blood flow image generating unit which generates aplurality of blood flow image data corresponding to the mutuallydifferent traveling time of the inflowing blood based on the pluralityof imaging data; and a cardiac function analysis unit which allowsobtaining blood flow information indicative of cardiac function of themyocardium based on the plurality of blood flow image data.
 2. Themagnetic resonance imaging apparatus according to claim 1, wherein thecardiac function analysis unit is configured to generate profiles ofblood signal intensity, corresponding to the plurality of blood flowimage data as the blood flow information.
 3. The magnetic resonanceimaging apparatus according to claim 2, wherein the cardiac functionanalysis unit is configured to generate 3-dimensional profiles of theblood signal intensity.
 4. The magnetic resonance imaging apparatusaccording to claim 1, wherein the cardiac function analysis unit isconfigured to generate, as the blood flow information, a blood flowinformation image for performing piecewise display of “signal intensityof an arbitrary cross-section of the plurality of blood flow image data”or “signal intensity difference between arbitrary cross-sections of theplurality of blood flow image data” with a plurality of segments.
 5. Themagnetic resonance imaging apparatus according to claim 1, wherein thecardiac function analysis unit is configured to generate cross-sectionalimage data for distinguishably displaying a lesion area based on signalintensity difference between the plurality of blood flow image data, asthe blood flow information.
 6. The magnetic resonance imaging apparatusaccording to claim 1, wherein the cardiac function analysis unit isconfigured to generate (a) a curve indicating a profile of signalintensity in an arbitrary linear region of interest of arbitrary one ofthe plurality of blood flow image data, or (b) a curve indicating aprofile of signal intensity difference between arbitrary linear regionsof interest of the plurality of blood flow image data, as the blood flowinformation.
 7. The magnetic resonance imaging apparatus according toclaim 1, wherein the cardiac function analysis unit is configured togenerate (a) a curve indicating a profile of signal intensity ofarbitrary one of the plurality of blood flow image data in selected oneof linear regions of interest set on a cross-section of the myocardium,or (b) a curve indicating a profile of signal intensity differencebetween the plurality of blood flow image data, as the blood flowinformation.
 8. The magnetic resonance imaging apparatus according toclaim 7, wherein the cardiac function analysis unit is configured toperform positional correction of the plurality of blood flow image databy using a reference position set at a border part between right andleft ventricles in each of myocardial cross-sections corresponding tothe plurality of blood flow image data, and to calculate the signalintensity difference between the plurality of blood flow image dataafter the positional correction.